1. Field of the Invention
The present invention relates to a setting tool for driving in fastening elements and including a piston guide having a hollow chamber, a setting piston axially displaceably arranged in the hollow chamber of the piston guide and having a piston head, a piston stem, a piston band, and a piston stop device for the setting piston and arranged in a setting direction end region of the hollow chamber, with the piston stop device having a damping element supported against a stop, and a stop member adjoining the damping element in the direction of the hollow chamber and operationally connectable with the piston band.
2. Description of the Prior Art
Setting tools of the above-described type are driven with solid, gaseous, or fluid fuels or with compressed air. In combustion-driven setting tools, the setting piston is driven by combustion gases. With these setting tools, fastening elements, such as, e.g., nails or bolts are driven in constructional components.
German Publication DE 3930592A1 discloses a setting tool in which a piston is guided in a piston guide that is axially displaceably arranged in a sleeve-shaped housing. For effecting a setting process, the setting tool should be pressed against a constructional component to press the piston guide into the housing. For reduction of the piston energy at false set-ups or when the piston is driven with an excessive energy forward into the piston guide, there is provided in an end region of the piston guide, an elastic annular member which intercepts the piston.
A drawback of this setting tool consists in that when the wear of the elastic annular member is too large and cannot be recognized, expensive tool components can be damaged. Further, the piston band which strikes the annular member should have as a large diameter as possible to prevent a premature destruction of the annular member. This increases the tool weight. For high-energy tool (above about 350J), the elastic annular member is unsuitable because the piston penetrates deeply into the elastic annular member, causing a strong wear of the rubber which leads to damage of the tool.
German Publication DE 19947464A1, from which the present invention proceeds, discloses a setting tool in which a sleeve-shaped thrust member that acts as a stop for the piston, is supported via an elastic annular buffer against a bolt guide. The thrust member has a conical opening expanding toward the piston band, with the diameter of the piston band being substantially larger than the inner diameter of the opening of the thrust member. During a stop process with the thrust member, the lower surface of the piston band engages an annual surface of the thrust member surrounding the opening.
A drawback of the setting tool of DE 19947464A1 is a high mass of the piston because of the large piston band diameter. Another drawback consists in that the allowable amount of the wear of the thrust member or of the buffer cannot be recognized by the user, which can lead to damage of tool components.
U.S. Pat. No. 4,828,003 discloses a setting tool in which between the piston guide and the bolt guide, there are arranged one after another a rigid ring and an elastic ring. In the elastic ring, a further rigid ring is arranged that limits the stroke of the first rigid ring. The first rigid ring has a bushing conically narrowing in the setting direction for the piston stem. The piston band surface of the setting piston adjacent to the first rigid ring, has a conical profile, and the conical profile of the piston band surface and the conical surface of the bushing are complementary to each other.
A drawback of the setting tool of U.S. Pat. No. 4,828,003 consists in that the allowable amount of the first ring wear cannot be recognized by the user, which again can lead to damage of the tool components.
An object of the present invention is to so modify the setting tool of the above-described type that the drawbacks of the prior art tools are eliminated and the damage of the tool components is prevented.
Another object of the present invention it to so modify the setting tool that wear of the piston stop or braking device above an allowable amount is recognized by the user.